i have dc, only aftermarket alternator i've owned, so i can only speak of my experience with that one
but, the guys at dc are awesome, i had a little hick-up with my alt (bought locally, had wrong pully and connection terminal) called dc, dude was just like, email me a picture of it, i'll tell ya what it is and what ya need, did it right on the phone with him, he instantly told me what it was, what i needed, credit card over the phone, total call time maybe 7-10 minutes, a couple days later, had the right parts, everythings gone smooth since then.
good guise over that at dc, and the alt has been great to me too